1. Field of the Invention
The invention concerns a needle bar drawing device (gill box for drawing card slivers, the device comprising a driven gilling area (needle field) of needle bars arranged independently of each other having cranks guided in a channel cam and arranged at least at one of their ends, and comprising slot guides for the needle bars, the slot guides determining the orbit of the needle bars during their total run and arranged on both sides of the gilling area.
2. Description of Prior Art
A needle bar drawing device of this species is known from German Letters Patent 165 597. This device which is called a push bar drawing equipment according to present terminology has needle bars guided in slot guides on both sides of the gilling area, which bars are controlled by cranks in respect of the position of the needles. The driving of the needle bars is performed by means of toothed discs or crown gears whose toothing protrudes into their path and which conveyingly engage some needle bars. The pitch of the toothed discs corresponds to that determined by the diameter of the bar body.
A device which corresponds in the essential details to the known device can also be taken from German Pat. Nos. 813 670 and 953 589 in which, however, the pitch of the needle bars is determined by spacer bodies arranged on their shafts.
In practice drawing equipments of this constructional type have a greater tendency to pitch change due to wearing which can be noticed in a disturbing manner by way of synchronisation problems when two gilling areas which engage or mesh with each other or when driven holding down means engaging the needles are used. Furthermore, the noise level increases very quickly and vigourously, especially when e.g. the usual efficiency is to be achieved in chain drawing equipment. The reason for this is that the conveying engagement of the toothed discs is only effective on those needle bars which are in contact with the toothed discs. The other needle bars must be pushed by these few directly driven needle bars against the slippage resistance resp. gliding friction which occurs in the crank guide and the guide path which determines the orbit, whereas in the working slack this pushing has to be performed via the spacer bodies against the drawing forces. This means that a resistance has to be overcome which corresponds to the sum value of the single resistances of all needle bars positioned between two driving points.
The endeavour to meet this deficiency finally led to the suggestion of a push bar drawing equipment which is described in German Pat. No. 1 057 507. In this embodiment the number of needle bars positively conveyed during their orbit is raised by the engagement of an additional pair of driven toothed discs which partly reduces the disclosed wearing characteristics without solving the problem satisfactorily.